Process for manufacturing carbureted water gas



March 13, 1934. M. MERRITT ET AL 1,950,620

PROCESS FOR MANUFACTURING CARBURETED WATER GAS Filed May 16. 1931 Patented Mar. 13, 1934 UNITED STATES PROCESS FOR MANUFACTURING CARBURETED WATER GAS Malcolm H. Merritt and George I. Koons, Fort Wayne, Incl, assignors to The Western Gas Construction Company, a corporation of Indiana Application May 16, 1931, Serial No. 537,969

4 Claims.

Our invention relates to the manufacture of carbureted water gas, and more particularly to the method of manufacturing carbureted water gas in which water gas, generated by the passage 5 of steam through a bed of incandescent carbonaceous fuel, is carbureted at elevated temperatures by the addition thereto of heavy oil.

As is well known, carbureted water gas is ordinarily made in an intermittent manner,

that is to say in a series of cycles, each'of which cycles comprises principally a blow or heating period, and a run or gas-making period. The blow or air-blast period is carried out by blasting a bed of carbonaceous fuel to incandescence,

removing the resultant air-blast gases and conducting them through carbureting apparatus, which generally comprises a carbureter and a superheater the interior of each of which is partially filled with checkerbrick.

During the passage of the air-b1ast gases through the carbureting apparatus, additional or secondary air is admitted, causing the combustion of the air-blast gases. In this manner the carbureting apparatus is brought to a high temperature by means of the heat of combustion or sensible heat of the air-blast gases.

In the subsequent steam run period, steam is passed through the incandescent fuel and all or a portion of the resultant water gas is conducted through the highly heated carbureting apparatus where oil is introduced to carburet and enrich the gas. This oil is vaporized, cracked, and finally fixed as a permanent gas in the stream of water gas, thereby forming carbureted water gas, which is then withdrawn for use as fuel or illuminating gas. This cycle of operation is repeated, carbureted water gas thus being produced intermittently.

At the present time the greatest problem confronting the manufacturers of carbureted water gas is the use of heavy oil, such as bunker oil.

The gas oils which have been used for carbureting purposes in the past are now becoming less available. By reason of these facts as well as the necessity of reducing manufacturing costs to a point where carbureted Water gas can successfully compete with natural gas, oil refinery gas and other gases now available, it has become of the greatest importance for the manufacturer of carbureted water gas to be able to employ for carbureting purposes inexpensive heavy oils of low grade, such as the so-called bunker oils.

However, when it has been attempted to use such oils for carbureting purposes in the man-' ufacture of carbureted water gas great diiiiculties have been encountered, the principal difficulties arising from the extremely high coke content and the low volatility of such oils. Carbureted water-gas processes which have been entirely satisfactory insofar as the use of gas oil having less than 1% coke content is concerned have proved entirely incapable of handling heavy fuel oils, the coke content of which ranges from 6% to 20%.

In instances where such oil has been substituted for gas oil in plants previously operating satisfactorily on gas oil, without other change in the process or apparatus, the carbon deposits formed in the carbureting apparatus have been so excessive that the passages through the checkerbrick of the carbureter and superheater became plugged with carbon deposit within a few hours, frequently necessitating shutting down the apparatus before one days operation had been completed.

Moreover, this shutting down was necessarily followed by removal and replacement of the checkerbrick in the carbureter, an expensive, tedious and time-consuming operation greatly increasing the manufacturing cost of the gas. Moreover in such instances the oil cracking efficiencies and fuel economies obtained have been poor.

It has been proposed to introduce a large por-* tion or all of the necessary oil directly into the top of the generator, combined with socalled marginal blasting of the upper portion of the fuel bed onto which the oil is sprayed, this marginal blasting being accomplished by introducing an additional or secondary forward-air-blast to the upper portion of the fuel bed. However, such marginal blasting methods have proved unsatisfactory and have not, to the bestof applicants knowledge, obtained any widespread use by reason of their known disadvantages.

Such reverse-air-blasting methods as have been suggested or employed in the past have been unsatisfactory for a number of reasons. The removal of reverse-air-blast gases at the top of the carbureter on generator is entirely unsatisfactory by reason of the great loss of fuel economy.

In order for an entirely satisfactory solution of the heavy oil problem to be accomplished, it is clear that the solution must be dominated by certain considerations. In the first place, the capacity of the set must not be decreased'and it must be possible to produce gas of satisfactory thermal value at proper oil and fuel economies.

The deposit of carbon in the carbureting ap paratus must be consumed automatically during the regular course of the cycle so that no shutdown periods for carbon removal are necessary. Moreover, the carbon deposit should be entirely utilized as fuel, and preferably in such manner as to assist in maintaining the desired high'temperature conditions in the generator fuel bed and carbureting apparatus.

The proper balance of temperature conditions throughout the set must be maintained in order to carefully avoid that operating condition which makes gas too high in heating value to be wasted and yet too high in inerts to. be delivered to the holder. Moreover, it is highly desirable to provide a cycle of gas-making operations in all portions or periods of which some useful purpose other than the mere removal of carbon is being accomplished.

In View of the above, therefore, the general object of our present invention is the provision of a process for the manufacture of carbureted water gas in which heavy oil is employed for carbureting purposes and which shall be free from disadvantages such as those set forth hereinabove and efiective to provide a solution for the problem of the utilization of heavy oil in the manufacture of carbureted water gas.

A further object of our invention is to provide a process for the manufacture of carbureted water gas from heavy oil in which carbon deposited from the heavy oil is removed during the ordinary cycle of operation without necessitating shut-down periods for the removal of such carbon from the apparatus, and without lengthening the cycle.

A third object of our invention is to provide a process for the manufacture of carbureted water gas from heavy oil in which carbon deposited from the heavy oil is advantageously employed as fuel in the regular course of the process.

A further object of our invention is to provide a process of the character indicated in which regulation of temperatures throughout the apparatus and more particularly in the fuel bed and carbureting apparatus within an eiiicient range is facilitated and in which improved fuel and oil economies may be obtained.

A still further object of our invention is to provide a method of the character indicated that is simple in operation and does not require inclusion of periods or operations of little utility in the operating cycle.

A still further object of our invention is to provide a process of the character indicated in which an optimum thermal or fuel economy is obtained.

Our invention has for further objects such other operative advantages and improvements as may hereinafter be found to obtain.

Our invention does not contemplate a departure from the fundamental water gas operating cycle of intermittent blow and run, although as will be apparent hereinbelow, the contemplated cycle or cycles of operation differ materially as to the nature, extent and sequence of various portions of the cycle as compared with prior cycles employed for the manufacture of carbureted water gas from gas oil and the like.

In the copending application of Gerald J. Nordmeyer and Thomas W. Stone, Serial No. 537,968 filed concurrently herewith, there is described an improved process for the manufacture of carbureted water gas from heavy oil. That process contemplates, among other things, the use of reverse-air-blast in a novel manner and to a novel extent.

It has been shown in the aforesaid application that this novel use of reverse-air-blast as an integral feature of the operating cycle, for example, in amount equal to from one-tenth to one-half of the total air requirement of the process, presents an effective and advantageous solution of the heavy oil problem. This is especially true when combined with the introduction of a part of the heavy oil used for carbureting the gas directly to the generator fuel bed and with the Withdrawal of the reverse-air-blast gases from an intermediate level just below the upper portion of the fuel bed the temperature of which is affected by said introduction of heavy oil thereto.

Our invention, which relates to a specific improvement of the process broadly disclosed and claimed in the aforesaid application of Stone and Nordmeyer, contemplates a g nerally similar use of reverse-air-blast, but combined with the introduction of all of the heavy oil used for carbureting the gas onto the top of the fuel bed. According to a particular operating sequence, this combination has been found to possess considerable merit from the standpoint of thermal economy, as will appear hereinbelow.

According to our invention, all of the heavy oil is introduced by spraying the same into the top of the generator fuel bed during the steamrun period and the steam-run period is followed, rather than preceded, by a reverse-air-blast period, in which the reverse-air-blast passes back through the carbureting apparatus and then through at least the upper portion of the fuel bed before being discharged to the atmosphere or to waste heat recovery apparatus.

As described in the aforesaid application, additional secondary air may be employed during the reverse-air-blast period, where so desired.

We have found that when the reverse-air-blast follows the steam-run, and more particularly the steam backrun period, and especially where all of the heavy oil is sprayed upon the generator fuel bed, the temperature conditions in the generator fuel bed are such as to favor the formation of carbon dioxide rather than carbon monoxide in the reverse-air-blast gases. This results in respect to the withdrawal of the reverse-airblast gases and the process as a whole.

In order that our invention may be fully set forth and understood we now describe with reference to the accompanying drawing the preferred manner and form in which our invention may be practiced and embodied. In this drawins,

Figure 1 is a view partly in elevation and partly in vertical section of apparatus for manufacturing carbureted water gas in accordance with the present invention, parts being more or less diagrammatically shown; and

Fig. 2 is a similar view of a modified form of a portion of the apparatus shown in Fig. 1.

Similar characters of reference designate similar parts in each or" the views of the drawing.

Referring to the drawing and more particularly to Fig. 1, there is shown a form of apparatus for manufacturing carbureted water gas comprising principally a generator 1, carbureting apparatus which in this instance comprises a carbureter 2 and a superheater 3, and a gas cfftake seal or tar batter 4. The generator 1 is provided with a grate 5 adapted to support a bed of carbonaceous fuel 6, and preferably, although not necessarily, with means such as a revolving beam '7 for continuously removing ash or clinker from the fuel bed 6. Fuel is introduced to the generator through a charging openin' 8, the introduction of the fuel being preferably, but not necessarily, accomplished by an automatic charging device 9 located immediately above the charging opening 8.

The upper portions of the generator 1 and improved thermal economy with 1135 the carbureter 2 are connected by means of a conduit 12, preferably so designed as to provide a permanently free passage for gas between the generator and carburetor. The carbureter 2 and the superheater 3 are connected through an open conduit 13. The interiors of the carbureter 2 and the superheater 3 are partially filled with checkerbrick 14 and 15, respectively, this checker-brick being preferably so spaced within the carbureter 2 and superheater 3 as to provide minimum obstruction to the flow of gas therethrough with maximum heat storage capacity.

The upper portion of the superheater 3 is provided with a stack T 16 having a stack valve 17 for discharge of gases to the atmosphere and also having, where so desired, a connection 18 having a valve 19 leading to a waste heat boiler or other waste heat recovery device (not shown). The top of the superheater 3 is provided with a conduit 21 leading to the gas olftake seal 1 and terminating below the level of the sealing liquid therein.

The base of the generator 1 is provided with a conduit 22 for introduction of gases into .or removal of gases from the generator fuel bed 6, as the case may be, the conduit 22 communicating with a conduit 23 which bypasses the carbureter 2 and superheater 3 and is provided with a stack connection 24 having a stack valve 25, and also with a connection 26 leading to the gas offtake seal 4 and terminating below the level of sealing liquid therein.

Within the gas oi ftake seal 4 there is provided a valve device 27 adapted to alternately and oppositely open and close the connections 21 and 26 in accordance with the desired sequence of operations. The gas oiftake seal 4 is also provided with a gas offtake 28 leading to a gas holder or to the distribution system. It will be understood that one purpose of the gas offtake seal 4 and valve 27 is to insure against passage of gas in a reverse direction from the gas offtake 28 into the carbureted water gas set and another purpose of the same is to provide for the reversal of fiow through the generator, carbureter and superheater.

In the drawing the valve 2'7 is shown in position for the passage of gas in a forward direction through the generator, carbureter and superheater in the order named and thence through the gas offtake seal 1 and gas offtake 28, while preventing flow of gas from the base of the generator to the gas offtake seal.

Air blast for the operation of the set is provided from an air-blast manifold 31 which is provided with a primary-air-blast pipe 32 having a valve 33 and leading through the connection 22 into the base of the generator 1, with a secondary-air-blast pipe 34 having a valve 35 and communicating with the conduit 12, or alternatively with the top of the carburetor 2. Also a reverse-air-blast pipe 36 has a valve 37 and communicates with the stack? 16, or alternatively leads directly into the upper portion of the superheater 3.

Heavy oil for carbureting purposes is supplied from suitable storage and heating facilities (not shown) through a conduit 41 having a valve 43 and leading to a spray 45 located in the top of the generator 1.

We further provide an uprun steam connection having a valve 51 and communicating through the connection 22 with the base of the generator 1, a backrun steam connection 52 having a valve 53 and communicating with the connection 21, or alternatively leading directly into the upper portion of the superheater 3. Also (for use when so desired), a downrun steam pipe 54 has a valve 55 and communicates with the upper portion of the generator 1, or alternatively with the connection 12.

The generator 1 is preferably, but not necessarily, provided as shown with a reverse-airblast offtake manifold communicating through a plurality of ports 61 with the generator fuel bed. The ports 61 may be of any desired number according to the size of the generator 1, and are preferably located on a circle located at an intermediate level of the fuel bed 6 and preferably from two to five feet below the top of the fuel bed, this level being readily determined by analysis of reverse-air-blast gases passing downward through the generator fuel bed 6 to determine that point at which said gases contain a minimum content of carbon monoxide.

In this connection it may be noted that variations in the depth of the generator fuel bed must be taken into account in locating the ports 61. Where mechanical charging apparatus is available and the generator is charged during every operating cycle the level of the top of the fuel bed 6 will remain fairly constant, but where hand-charging is practiced and relatively large amounts of fuel are charged at comparatively widely separated intervals of several cycles the level of the top of the fuel bed 6 may vary considerably.

In any event, however, the ports 61 will be valve 65 and leading to a suitable waste-heat boiler or other waste-heat recovery apparatus (not shown).

With respect to the aforesaid apparatus, we now describe for purposes of illustration a preferred operating cycle according to which the process of our present invention may be advantageously carried out. This cycle consists of the following periods and operations set forth hereinbelow.

1. Forward-air-blast period During this period all steam and oil valves are closed, as are the auxiliary stack valves 25 and 63, while the reversing valve 27 is held in the position in which it is shown in the drawing.

The reverse-air-blast valve 37 is also closed, the primary-air-blast valve 33 being open. Air is admitted to the base of the generator 1 and passes upward through the fuel bed 6. The resultant air-blast gases then pass through the i.-.-;:--..

generator-carbureter connection 12 to the top of the carbureter 2.

After the first few seconds of this period additional air is admitted by opening the secondary-air-blast valve 35 to admit at least 811-1 cient air to cause the combustion of substanially all of the carbon monoxide content of .the air-blast gases coming from the generator 1.

The resultant air-blast gases and gases of combustion pass downward through the carbureter 2, through the connection 13, upward through the superheater 3, meantime yielding the greater portion of their heat of combustion and sensible heat to the checkerbrick 14 and 15, and finally pass through the open stack valve 17 into the atmosphere or through the open valve 19 and connection 18 to the waste heat boiler (not shown).

When the desired temperature conditions, as determined largely by the nature of the heavy oil to be employed for carbureting purposes, have been attained, the forward-air-blast period is discontinued, and a steam run period then follows which is divided into two periods, the first of which is a steamuprun period.

This change is accomplished by closing the air-blast valves 33 and 35 and the stack valve 17 (or valve 19 as the case may be) and opening the steam valve 51.

Due to the fact that the carbon monoxide content of the air-blast gases tend to rise during the forward-air-blast period, a short blow-run period may be accomplished at this point, when so desired, by closing only valves 35 and 17 or 19 while holding valve 33 open. The air-blast gases, rich in carbon monoxide thus pass to the gas ofitake 28 and are included in the make. After a suitable time, the air-blast valve 33 is closed and the steam valve 51 is opened.

Where a blow-run period is not desired, the sequence of operation is reversed, valves 33 and 35 first being closed and valve 51 opened, while the valve 17 or 19 is not closed until substantially all of the air-blast gases are purged from the set.

2. Steam uprun period All stack. valves and air valves now being closed and the reversing valve 2'7 in the position in which it is shown in the drawing, steam is admitted to the base of the generator 1 through the steam uprun valve 51.

The steam passes upward through the generator fuel bed 6, the resultant water gas being conducted through the connection 12 into the carburetor 2 and then passes through the carbureter 2, connection 13, superheater 3 and connection 21 to the gas oiftake seal 4 and out through the gas offtalze 28..

During substantially the whole of this period, heavy oil, preferably at a high temperature and considerable pressure is introduced through the spray 45 to the top of the generator 1. For example we may employ a temperature or" 2G0 F. and a pressure of 225 pounds per square inch or such pressure and temperature as are necessary in order to provide a proper flow of oil. The heavy oil discharges upon the highly heated upper portion of the generator fuel bed 6, and during the course of this introduction and discharge being volatilized and cracked. The resultant oil gases and vapors commingle with the water gas coming from the generator fuel bed 6 and are permanently fixed by contact with the highly heated checkerbricl; 15 within the carbureter 2 and superheater 3.

As this is the only portion of the cycle in which oil can be admitted for carbureting purposes without reducing the specific gravity of the final gas, it is necessary, except in the instance noted hereinbelow, to accomplish a suificient carburetion of the uprun water gas pro duced during this period to so provide that the ultimate mixture of carbureted and uncarbureted gases passing through the gas ofitake 28 during the entire course of the cycle is of suflicient calorific value, for example from 500 to 530 B. t. u. per cubic foot.

Some carbon will be deposited during this period in the carbureter 2 from oil vapor or oil particles carried'over from the generator 1 by the uprun water gas, but this carbon deposit is small in amount as compared with that which would be obtained if heavy oil were introduced directly to the carbureter 2.

It will be obvious to those skilled in the art that in the present instance, the chamber 2 plays the part of a superheater or fixer rather than that of a true carburetor. However, in view of the general similarity of the apparatus to that of the prior art, the term carburetor, rather than superheate1", is sometimes employed herein to designate the chamber 2.

In order to maintain the proper conditions within the generator fuel bed it is ordinarily necessary or desirable to reverse the direction of steam fiow to the generator fuel bed during a considerable portion of the total steam run. This is preferably accomplished by following the foregoing period with a steam backrun period.

3. Steam baclcrun or down/run period In going from the steam uprun period to a steam backrun period the uprun steam valve 51 is closed, the reversing valve 27 is placed in a position opposite to that in which it is shown in the drawing, and the backrun steam valve 53 is opened. Steam now flows through the backrun steam connection 52 and the connection 21 into the. top of the superheater 3 and passes downward through the superheater 3 to the connection 13 and upward through the carbureter 2. During the course of the backrun steam it becomes highly superheated by contact with the checirerbrick 15 and 14 within the superheater 3 and carbureter 2, respectively, and may also react with any small quantities of carbon remaining upon the checkerbrick 15 or 14 to form water gas, thereby partially consuming such carbon.

The resultant highly superheated backrun steam which may include small quantities of water gas produced in the manner just described, then passes through the connection 12 into the top of the generator 1 and passes downward through the generator fuel bed 6. The resultant backrun water gas then passes from the base of the generator 1 through the connections 22, 23 and 26 into the gas offtake seal 4 and is withdrawn through the gas oiftake 28 and commingled with water gas and blow run gas produced during other portions of the cycle.

Where the specific gravity of the final gas is otherwise somewhat high, it may be desirable to introduce heavy oil to the generator fuel bed during this period. By reason of the fact that the oil vapors and gas thus produced are carried downward through the heated fuel bed and are subjected to considerable cracking the effect The steam backrun or downrun" period is then followed by a reverse-air-blast period. 4. Reoerse-air-blast period The valve 2'7 being in the position occupied. during the previous steam backrun period, valve 53 is closed and reverse-air-blast is admitted to the top of the superheater 3 by opening the reverse-air-blast valve 37. Grdinarily, for the first few seconds of this period, the stack valve and also the stack valve 63, (and valve if provided,) are held in the closed position to effect a blow-run or purge of water gas and steam remaining in the set. V

The reverse-air-blast passes downward through the superheater 3, becoming highly superheated through contact with the checkerbrick l5 and causing the combustion of any carbon deposited thereon and then passes in this highly heated condition through the connection 13 into the carbureter 2.

Passing upward through the checkerbrick 14 within the carbureter 2 the reverse-air-blast gases cause the combination of any carbon deposited upon the checkerbrick 14 during the previous steam uprun period, and not consumed in the previous steam backrun period. The resultant reverse-air-blast gases pass through the generator-carbureter connection 12 into the generator 1 driving ahead of them any steam and water gas remaining in the set, which water gas may, as indicated above, for a brief purge period of a few seconds be withdrawn through the gas oiftake 28 and commingled with carbureted water gas produced during other portions of the cycle.

As soon as this brief blow run or purge period is accomplished the stack valve 25 or the stack valve 63, (or if a waste heat boiler is provided, the valve 65) is opened, thus permitting the discharge of the reverse-air-blast gases to the atmosphere, or to the waste heat boiler as the case may be.

As hereinabove set forth, the stack valve 63 or the valve 65 may be employed for this purpose rather than the stack valve 25, wherever the reverse-air-blast gases after passing through the upper portion only of the fuel bed 6 contain a minumum carbon monoxide content. In the upper portion of the fuel bed during the reverseair-blast period the reactions favor the formation of carbon dioxide, whereas if the reverseair-blast gases are permitted to traverse the entire fuel bed, carbon dioxide present in the reverse-air-blast gases entering the generator 1 or formed during the passage of the reverseair-blast gases through the upper portion of the fuel bed 6 may be converted in part to carbon monoxide in the lower portion of the fuel bed, thus producing a gas which might contain more carbon monoxide than is desirable.

By reason of the fact that the temperatures of the fuel bed and carbureting apparatus are lower at the conclusion of the steam backrun or downrun period than at any other time during the cycle, and also by reason of the fact that all of the heavy oil used for carbureting the gas is introduced by spraying it upon the generator fuel bed, thus still further reducing thetemperature of the latter and especially the upper portion thereof, the performance of the reverse-air-blast period at this time in the cycle is of especial advantage.

In the first place, the lower temperatures which prevail result in the removal from the set of much less sensible heat, thereby effecting an improved th rmal economy. In the second place, the reactions in the fuel bed at this time tend to favor the formation of carbon dioxide rather than carbon monoxide, so that the reverse-airblast gases issue from the fuel bed lower in carbon monoxide, which also effects an important thermal economy.

Moreover, the fact that the carbon resulting from the introduction of the oil is substantially entirely deposited in the fuel bed, in addition to providing for cleaner carbureting apparatus, provides for a higher free oxygen content in the reverse-air-blast gases entering the generator. For this reason, the consumption of the carbon deposit by the reverse-air-blast is facilitated, and the carbon deposit is utilized as fuel in the generator, where it can be handled to the best advantage.

During this period, as hereinabove set forth, at least sufficient air is employed to insure the combustion of any carbon deposited within the A carbureting apparatus, and to' cause sufficient combustion in the upper portion of the fuel bed 6 to balance the heat reduction caused by the introduction of heavy oil to the top of the generator during the cycle.

If desired, just before the conclusion of this reverse-air-blast period the stack valve 25 or the stack valve 63 or the valve 65 (depending upon which one of these valves has been in the open position) may be closed, thus providing for a brief blow run period in which the reverseair-blast gases (which at this time may contain considerable quantities of carbon monoxide) are permitted to pass through the connections 22, 23 and 26 into the gas offtake seal 4 and out through the gas oiftake 28 to be commingled with carbureted water gas produced during other portions of the cycle.

The introduction of air during the reverseair-blast period with the above in view may be accomplished solely through the reverse-air-blast connection 36 and valve 37, but in certain instances it may be desirable to introduce through the connection 36 only sufficient air to insure the combustion of carbon within the carbureting apparatus or to effect a sufficient preheating of all of the reverse-air-blast employed, and to introduce such additional air through the connection 34 and the secondary air blast valve 35, which may be opened for this purpose, as may be necessary to cause the desired combustion in the top of the generator fuel bed 6.

This mode of operation avoids the passage of excessive air through the carbureting apparatus, thus eliminating any undesirable cooling effect upon the carbureting apparatus which might be caused by excess air and also reducing the total back pressure exerted by the apparatus upon the reverse-air-blast, which in turn makes it possible to blast more air through the apparatus in a shorter time.

While it will be obvious to those skilled in the art that the actual quantities of air, steam and oil and the length'of the various periods of the cycle will depend upon factors varying from set to' set and from plant to plant, nevertheless the following summary of operating conditions in one actual installation will be of value as illustrative of the practice of our present invention. These figures are based upon actual operation of a standard carbureted-water-gas set having a nine-foot generator and equipped with connections for reverse-air-blast and backrun steam, but not in this instance provided with the reverse-air-blast offtake located at an intermediate point of the fuel bed, as shown at 60 and 61 in the drawing.

1 .-Forward-air-blast:

Primary air 60 seconds at .9500 cu. ft. per

minute Secondary air 52 seconds at 2300 cu. ft. per

minute 2.Im'tial steam uprun:

88 seconds at 145# ofsteam per'minute 3.Steam backrun:

60 seconds at 135# of steam per minute 4.Reverse-air-blast:

(a) Blow run 4 seconds at 5500 cu. ft. of air per minute (1)) Reverse-air-blast to stack 35 seconds at 6000 cu. ft. of air per minute Blow run 6 seconds at 5500 cu. ft. of air per minute While the above figuresrepresent an actual operating instance and are believed to be relevant as disclosing to a considerable extent the actual nature of a satisfactory cycle, they are not to be taken as necessarily indicative of the best results obtainable by means of one-process or-as establishing a fixed rule forthe operation of other apparatus under different conditions,

) as will readily be appreciated by those skilled in the art.

In any event the cycle employed difiers materially from a cycle which would be'satisfactory when using gas oil for carbureting purposes in the same apparatus, this difference residing principally in the manner of introduction of the heavy oil and the extent and duration of the reverse-air-blast period as well as in the disposition of the resultant gases. stance of a cycle used in the prior art for-the manufacture of carbureted water gas from gas oil, we may cite the following:

1 .-'Forward-air-blast 105 seconds at 7500 cu. ft. of air per minute including 97 seconds carbureter blast at 3300 cu. ft. of air per minute 2.--Reverse-air-blast (blow run) .8 seconds at 4500 cu. ft. of air per minute 3.Initial steam uprun:

70 seconds at 130# of steam per minute 4.Steam backrun:

"71 seconds at 140# of steam per minute 12 seconds at 130# of steam per minute 6.Purye:

seconds at 6700 cu. ft. of air per minute The latter cycle could not be employed in conjunction with the use of heavy oil for carbureting purposes, because it makes no provision for the-use'of heavy oil in the generator.

.In the present instance, we prefer to employ a reverse-air-blast equal in amount to form onetenth to one-half of the total air requirement of the process, depending principally upon the nature of the heavy oil used. The greater portion or all of the reverse-air-blast gases thus produced are discharged to the atmosphere or delivered-to waste heat recovery apparatus. In general, the total air requirement of the process (which includes both forwardand reverse-airblasting, and-both primary and secondary air) will not difier materially from the air requirement of the conventional carbureted water-gas process of the past, in which gas oil was used As a typical in-- for carbureting purposes and about to 40 cu. ft. of air per pound of steam were employed.

By reason of the fact that the amount of reverse-air-blast according to our process constitutes a large portion of the total air-blasting or blow period, it will be obvious that where the reverse-air-blast gases are removed through the ports 61 and the manifold connection 60, the air-steam ratio insofar as the lower portions of the fuel bed 6 are concerned may be considerably lower than that employed heretofore. Our experience has indicated that this does not always have a harmful effect upon generator fuel bed conditions, but where it is desired to'maintain the lower portion of the fuel bed at a high temperature and still retain the advantages of removing the reverse-air-blas-t gases at an intermediate level in the fuel bed, and especially where a self-clinkering grate-device is employed, a regenerator may be placed in the connection 22 contiguous to the base of the generator 1.

Such a regenerator is efiective to absorb heat from the gases leaving the base of the generator and to transfer such heat to air or steam about to enter the generator for upward passage through the fuel bed 6. Either the primary-airblast alone or the uprun steam alone or both may be passed through this regenerator which is thus particularly effective where a self-clinkering grate device is employed and there is no relatively large and cool ash zone at the bottom of the fuel bed 6.

To provide for increasing the air-steam ratio in the bottom of the fuel bed during a reverseair-blast periodin which the air-blast gases are withdrawn through the ports 61 and the manifold and pass out through the stack valve 63 to the atmosphere or through the valve '65 to the waste heat boiler, as the case may be, we may however employ a simultaneous forward blast through the lower portion of the generator.

Accordingto this modification, during the first part of the forward-air-blast period, when air blast is being introduced to the bottom of the generator through the valve 33, air-blast is simultaneously introduced to the top of the superheater through the valve 37. The air-blast from the valve 33 passes upward through the fuel bed to the level of the ports 61 where it meets the reverse-air-blast introduced through the valve 37 and the combined forward-airblast and reverse-air-blast gases pass through the connection 62 to the atmosphere or to the waste heat boiler, as desired.

Where this simultaneous forwardand reverse-air-blast is contemplated, the type of reversing valve shown at12'7 in Fig. 1 cannotbe employed and it necessary in this instance to employ a valve arrangement for the conduits 21 and 26 which is capable of positively closing either one of these conduits, while the other remains open, and also of positively closing both conduits simultaneously. In Fig.2 we have illustrated suitable apparatus for this purpose. In thisapparatus, the reversing valve .27 is dispensed with and separate valves '70 and 71 are provided in the conduits 21 and 26, respectively.

During the first part of the air-blast period, when for\vard-air-blast and reverse-air-blast are simultaneously employed as just described hereinabove, both valves and 71 are closed. Later, when 'forward air-blasting is employed alone and during the steam uprun period, the valve71 in conduit 26 is closed while the valve 70 in conduit 21 may be kept open. When reverse-air-blasting alone is employed and during a steam backrun or downrun period, the valve is closed and the valve 71 is kept open.

When this procedure is followed, it will be obvious that the operating cycle can be considerably shortened because of the fact that the reverse-air-blast period overlaps the first part of the forward-air-blast period, which in turn greatly increases the capacity of the set as compared with operating conditions when forward-air-blasting and reverse-air-blasting are conducted separately. The cycle would then be as follows:

1.Air-blast period:

(a) Combined forward-air-blast and reverseair-blast (b) Forward-air-blast alone 2.Stedm uprun period. 3.Steam backrun or downrun period. 4.-Steam uprun (purge) period Obviously, since one cycle follows another, the combined reverse-air-blast and forward-air-blast period follows a steam backrun or downrun period after merely a short purging operation. In this manner, the advantages of having the reverse-air-blast follow the steam run period may be obtained without lowering the capacity of the set and with maximum thermal economy.

By operating in accordance with our present invention it is possible to make carbureted water gas of satisfactory thermal value and specific gravity from heavy oil, at low cost and with high fuel and oil economies. The checkerbrick in the carbureter and superheater are kept clean, the carbon deposit obtained from the oil is utilized to great advantage as fuel, a better balance of temperature conditions in the set is maintained, and gas of relatively low specific gravity can be made without sacrifice of thermal economy.

Moreover, the operation of valves and more particularly the tar batter reversing valve, is considerably simplified, thus resulting in less time consumed in valve operation, and hence higher capacity.

It will be apparent from the above that our invention accomplishes the various objects set forth hereinabove, making it possible to manufacture carbureted water gas from heavy oil with exceptionally good oil and fuel economy and numerous other advantages while avoiding disadvantages inherent in the methods and apparatus of the prior art. For the reasons set forth above the utility of our invention is therefore exceedingly great.

t will be apparent to those skilled in the art that our invention is not limited to the details of the specific apparatus or methods set forth hereinabove by way of illustrative example but is to be construed as of the scope of the claims hereinafter made.

We claim as our invention:

1. In the process of making carbureted water gas using heavy hydrocarbons as the carbureting medium in a set comprising a generator containing a bed of incandescent fuel, and a heat exchanger, the steps of introducing all of the hydrocarbon on the top of the fuel bed, followed by a reverse air blast through the heat exchanger and downwardly through the top portion only of the fuel bed.

2. The process of manufacturing carbureted water gas in an apparatus comprising a generator containing a bed of incandescent fuel, and a heat exchanger, which consists in the following separate, successive steps: first blasting said fuel bed with air and passing the products of combustion into the heat exchanger; then passing steam upwardly through said incandescent fuel bed to make gas, and introducing heavy hydrocarbons into said generator during the passage of steam through said fuel bed to enrich the gas and passing said gas into said heat exchanger; then passing steam through the heat exchanger and thence downwardly through said fuel bed and introducing heavy hydrocarbons into said generator during such downrun to make carbureted water gas; and then passing air in a reverse direction through said heat exchanger to superheat the air and thence downwardly through the fuel bed in said generator to consume carbon deposits in said fuel bed resulting from the admission of said heavy oil to said generator during the steam runs.

3. The process of manufacturing carbureted water gas in an apparatus comprising a generator containing a bed of incandescent fuel, and a heat exchanger, which consists in passing steam through said incandescent fuel bed to make gas and introducing heavy hydrocarbons into said generator during the passage of steam through said generator for carbureting said gas, all of the heavy hydrocarbons for carbureting said gas being introduced directly into said generator; and passing said carbureted gas into said heat exchanger; and then passing air in a reverse direction through said heat exchanger to superheat the air and thence downwardly through a portion only of the fuel bed in the generator to consume carbon deposits in said fuel bed resulting from the admission of heavy oil to said generator during the steam run; and. withdrawing said reverse air blast from said generator at a point intermediate of said fuel bed.

4. The process of manufacturing carbureted water gas in an apparatus comprising a generator containing a bed of incandescent fuel, and a heat exchanger, which consists in first blasting said fuel bed forwardly with air to highly heat the same and passing the products of combustion into the heat exchanger; then passing steam through said incandescent fuel bed first in an upward and then in a downward direction to make gas, and introducing heavy hydrocarbons into said generator during the passage of steam in an upward direction through said fuel bed to carburet the gas, all of the heavy hydrocarbons for carbureting said gas being introduced directly into said generator; and passing said carbureted gas into said heat exchanger; and then passing air in a reverse direction through said heat exchanger to superheat the air and thence, downwardly through a portion only of the fuel bed in the generator to consume carbon deposits in said fuel bed resulting from the admission of said heavy oil to said generator during the steam run; and withdrawing said reverse air blast from said generator at an intermediate portion of said fuel bed.

MALCOLM H. MERRITT. GEORGE I. KOONS. 

